For aircraft with retractable landing gear, each landing gear assembly typically includes a number of pin joint assemblies that allow separate elements of the landing gear assembly to pivot about the pin joint. Pin joints will typically be included in the side-stay assemblies to allow the upper and lower elements of the side-stay to pivot both with respect to one another and with respect to the main sliding tube of the landing gear and the aircraft frame itself.
As the landing gear assembly can experience both lateral and longitudinal loadings during take-off and landing events it is normal for some deflection to occur in the lugs of the side-stays through which the pin joint passes. Such deflections are exacerbated in modern side-stay designs, which exhibit complex geometry to accommodate other landing gear elements, such as springs and hydraulics, in order to reduce air resistance and the risk of bird strike when the gear is deployed. At present, the forces induced as a result of these lug deflections are reacted by the headed pin and nut or end cap of the pin joint assembly that passes through the lugs and allows the relative rotation of the two side-stay elements. Consequently, the headed pin and nut or end cap must be designed to be capable of carrying these deflection loads, with the necessary safety margin provided. To achieve this increased load carrying capability, the mass of the pin joint assembly is increased considerably. For example, for a mid sized commercial aircraft, this weight difference is typically around 2.5 kg per pin joint. On dual stay landing gear assembly for such an aircraft with six pin joints, approximately 15 kg may be added to the mass of each landing gear assembly simply to provide the requisite additional load carrying capability of the pin joint assemblies. In addition to the increased manufacturing cost arising from the larger pin joint assemblies, this added weight is undesirable in terms of the overall weight of the aircraft as it has a direct bearing on the fuel efficiency of the aircraft. It would therefore be desirable to reduce the weight of a pin joint assembly without compromising its load carrying capability.